/*
 * Copyright (c) 1999, 2010, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 */

package javax.sound.sampled;

/**
 * The <code>Line</code> interface represents a mono or multi-channel
 * audio feed. A line is an element of the digital audio
 * "pipeline," such as a mixer, an input or output port,
 * or a data path into or out of a mixer.
 * <p>
 * A line can have controls, such as gain, pan, and reverb.
 * The controls themselves are instances of classes that extend the
 * base <code>{@link Control}</code> class.
 * The <code>Line</code> interface provides two accessor methods for
 * obtaining the line's controls: <code>{@link #getControls getControls}</code> returns the
 * entire set, and <code>{@link #getControl getControl}</code> returns a single control of
 * specified type.
 * <p>
 * Lines exist in various states at different times.  When a line opens, it reserves system
 * resources for itself, and when it closes, these resources are freed for
 * other objects or applications. The <code>{@link #isOpen()}</code> method lets
 * you discover whether a line is open or closed.
 * An open line need not be processing data, however.  Such processing is
 * typically initiated by subinterface methods such as
 * <code>{@link SourceDataLine#write SourceDataLine.write}</code> and
 * <code>{@link TargetDataLine#read TargetDataLine.read}</code>.
 * <p>
 * You can register an object to receive notifications whenever the line's
 * state changes.  The object must implement the <code>{@link LineListener}</code>
 * interface, which consists of the single method
 * <code>{@link LineListener#update update}</code>.
 * This method will be invoked when a line opens and closes (and, if it's a
 * {@link DataLine}, when it starts and stops).
 * <p>
 * An object can be registered to listen to multiple lines.  The event it
 * receives in its <code>update</code> method will specify which line created
 * the event, what type of event it was
 * (<code>OPEN</code>, <code>CLOSE</code>, <code>START</code>, or <code>STOP</code>),
 * and how many sample frames the line had processed at the time the event occurred.
 * <p>
 * Certain line operations, such as open and close, can generate security
 * exceptions if invoked by unprivileged code when the line is a shared audio
 * resource.
 *
 * @author Kara Kytle
 * @see LineEvent
 * @since 1.3
 */
public interface Line extends AutoCloseable {

  /**
   * Obtains the <code>Line.Info</code> object describing this
   * line.
   *
   * @return description of the line
   */
  public Line.Info getLineInfo();

  /**
   * Opens the line, indicating that it should acquire any required
   * system resources and become operational.
   * If this operation
   * succeeds, the line is marked as open, and an <code>OPEN</code> event is dispatched
   * to the line's listeners.
   * <p>
   * Note that some lines, once closed, cannot be reopened.  Attempts
   * to reopen such a line will always result in an <code>LineUnavailableException</code>.
   * <p>
   * Some types of lines have configurable properties that may affect
   * resource allocation.   For example, a <code>DataLine</code> must
   * be opened with a particular format and buffer size.  Such lines
   * should provide a mechanism for configuring these properties, such
   * as an additional <code>open</code> method or methods which allow
   * an application to specify the desired settings.
   * <p>
   * This method takes no arguments, and opens the line with the current
   * settings.  For <code>{@link SourceDataLine}</code> and
   * <code>{@link TargetDataLine}</code> objects, this means that the line is
   * opened with default settings.  For a <code>{@link Clip}</code>, however,
   * the buffer size is determined when data is loaded.  Since this method does not
   * allow the application to specify any data to load, an IllegalArgumentException
   * is thrown. Therefore, you should instead use one of the <code>open</code> methods
   * provided in the <code>Clip</code> interface to load data into the <code>Clip</code>.
   * <p>
   * For <code>DataLine</code>'s, if the <code>DataLine.Info</code>
   * object which was used to retrieve the line, specifies at least
   * one fully qualified audio format, the last one will be used
   * as the default format.
   *
   * @throws IllegalArgumentException if this method is called on a Clip instance.
   * @throws LineUnavailableException if the line cannot be opened due to resource restrictions.
   * @throws SecurityException if the line cannot be opened due to security restrictions.
   * @see #close
   * @see #isOpen
   * @see LineEvent
   * @see DataLine
   * @see Clip#open(AudioFormat, byte[], int, int)
   * @see Clip#open(AudioInputStream)
   */
  public void open() throws LineUnavailableException;


  /**
   * Closes the line, indicating that any system resources
   * in use by the line can be released.  If this operation
   * succeeds, the line is marked closed and a <code>CLOSE</code> event is dispatched
   * to the line's listeners.
   *
   * @throws SecurityException if the line cannot be closed due to security restrictions.
   * @see #open
   * @see #isOpen
   * @see LineEvent
   */
  public void close();


  /**
   * Indicates whether the line is open, meaning that it has reserved
   * system resources and is operational, although it might not currently be
   * playing or capturing sound.
   *
   * @return <code>true</code> if the line is open, otherwise <code>false</code>
   * @see #open()
   * @see #close()
   */
  public boolean isOpen();


  /**
   * Obtains the set of controls associated with this line.
   * Some controls may only be available when the line is open.
   * If there are no controls, this method returns an array of length 0.
   *
   * @return the array of controls
   * @see #getControl
   */
  public Control[] getControls();

  /**
   * Indicates whether the line supports a control of the specified type.
   * Some controls may only be available when the line is open.
   *
   * @param control the type of the control for which support is queried
   * @return <code>true</code> if at least one control of the specified type is supported, otherwise
   * <code>false</code>.
   */
  public boolean isControlSupported(Control.Type control);


  /**
   * Obtains a control of the specified type,
   * if there is any.
   * Some controls may only be available when the line is open.
   *
   * @param control the type of the requested control
   * @return a control of the specified type
   * @throws IllegalArgumentException if a control of the specified type is not supported
   * @see #getControls
   * @see #isControlSupported(Control.Type control)
   */
  public Control getControl(Control.Type control);


  /**
   * Adds a listener to this line.  Whenever the line's status changes, the
   * listener's <code>update()</code> method is called with a <code>LineEvent</code> object
   * that describes the change.
   *
   * @param listener the object to add as a listener to this line
   * @see #removeLineListener
   * @see LineListener#update
   * @see LineEvent
   */
  public void addLineListener(LineListener listener);


  /**
   * Removes the specified listener from this line's list of listeners.
   *
   * @param listener listener to remove
   * @see #addLineListener
   */
  public void removeLineListener(LineListener listener);


  /**
   * A <code>Line.Info</code> object contains information about a line.
   * The only information provided by <code>Line.Info</code> itself
   * is the Java class of the line.
   * A subclass of <code>Line.Info</code> adds other kinds of information
   * about the line.  This additional information depends on which <code>Line</code>
   * subinterface is implemented by the kind of line that the <code>Line.Info</code>
   * subclass describes.
   * <p>
   * A <code>Line.Info</code> can be retrieved using various methods of
   * the <code>Line</code>, <code>Mixer</code>, and <code>AudioSystem</code>
   * interfaces.  Other such methods let you pass a <code>Line.Info</code> as
   * an argument, to learn whether lines matching the specified configuration
   * are available and to obtain them.
   *
   * @author Kara Kytle
   * @see Line#getLineInfo
   * @see Mixer#getSourceLineInfo
   * @see Mixer#getTargetLineInfo
   * @see Mixer#getLine <code>Mixer.getLine(Line.Info)</code>
   * @see Mixer#getSourceLineInfo(Line.Info) <code>Mixer.getSourceLineInfo(Line.Info)</code>
   * @see Mixer#getSourceLineInfo(Line.Info) <code>Mixer.getTargetLineInfo(Line.Info)</code>
   * @see Mixer#isLineSupported <code>Mixer.isLineSupported(Line.Info)</code>
   * @see AudioSystem#getLine <code>AudioSystem.getLine(Line.Info)</code>
   * @see AudioSystem#getSourceLineInfo <code>AudioSystem.getSourceLineInfo(Line.Info)</code>
   * @see AudioSystem#getTargetLineInfo <code>AudioSystem.getTargetLineInfo(Line.Info)</code>
   * @see AudioSystem#isLineSupported <code>AudioSystem.isLineSupported(Line.Info)</code>
   * @since 1.3
   */
  public static class Info {

    /**
     * The class of the line described by the info object.
     */
    private final Class lineClass;


    /**
     * Constructs an info object that describes a line of the specified class.
     * This constructor is typically used by an application to
     * describe a desired line.
     *
     * @param lineClass the class of the line that the new Line.Info object describes
     */
    public Info(Class<?> lineClass) {

      if (lineClass == null) {
        this.lineClass = Line.class;
      } else {
        this.lineClass = lineClass;
      }
    }


    /**
     * Obtains the class of the line that this Line.Info object describes.
     *
     * @return the described line's class
     */
    public Class<?> getLineClass() {
      return lineClass;
    }


    /**
     * Indicates whether the specified info object matches this one.
     * To match, the specified object must be identical to or
     * a special case of this one.  The specified info object
     * must be either an instance of the same class as this one,
     * or an instance of a sub-type of this one.  In addition, the
     * attributes of the specified object must be compatible with the
     * capabilities of this one.  Specifically, the routing configuration
     * for the specified info object must be compatible with that of this
     * one.
     * Subclasses may add other criteria to determine whether the two objects
     * match.
     *
     * @param info the info object which is being compared to this one
     * @return <code>true</code> if the specified object matches this one, <code>false</code>
     * otherwise
     */
    public boolean matches(Info info) {

      // $$kk: 08.30.99: is this backwards?
      // dataLine.matches(targetDataLine) == true: targetDataLine is always dataLine
      // targetDataLine.matches(dataLine) == false
      // so if i want to make sure i get a targetDataLine, i need:
      // targetDataLine.matches(prospective_match) == true
      // => prospective_match may be other things as well, but it is at least a targetDataLine
      // targetDataLine defines the requirements which prospective_match must meet.

      // "if this Class object represents a declared class, this method returns
      // true if the specified Object argument is an instance of the represented
      // class (or of any of its subclasses)"
      // GainControlClass.isInstance(MyGainObj) => true
      // GainControlClass.isInstance(MySpecialGainInterfaceObj) => true

      // this_class.isInstance(that_object)       => that object can by cast to this class
      //                                                                          => that_object's class may be a subtype of this_class
      //                                                                          => that may be more specific (subtype) of this

      // "If this Class object represents an interface, this method returns true
      // if the class or any superclass of the specified Object argument implements
      // this interface"
      // GainControlClass.isInstance(MyGainObj) => true
      // GainControlClass.isInstance(GenericControlObj) => may be false
      // => that may be more specific

      if (!(this.getClass().isInstance(info))) {
        return false;
      }

      // this.isAssignableFrom(that)  =>  this is same or super to that
      //                                                          =>      this is at least as general as that
      //                                                          =>      that may be subtype of this

      if (!(getLineClass().isAssignableFrom(info.getLineClass()))) {
        return false;
      }

      return true;
    }


    /**
     * Obtains a textual description of the line info.
     *
     * @return a string description
     */
    public String toString() {

      String fullPackagePath = "javax.sound.sampled.";
      String initialString = new String(getLineClass().toString());
      String finalString;

      int index = initialString.indexOf(fullPackagePath);

      if (index != -1) {
        finalString = initialString.substring(0, index) + initialString
            .substring((index + fullPackagePath.length()), initialString.length());
      } else {
        finalString = initialString;
      }

      return finalString;
    }

  } // class Info

} // interface Line
